Abstract
1. 1. Aminopyridines (APs) induced the release of [ 3H]dopamine ( 3H-DA) from rat synaptosomal preparations. 2. 2. 4-AP and 3,4-DAP were of equal efficacy in inducing release of 3H-DA; 3-AP, 2-AP and 2,6-AP were less active; pyridine and pyridine-4-carboxylamide were inactive. 3. 3. Cd 2+ was more effective in inhibiting 4-AP-induced release of 3H-DA (IC 50 ≈ 4 μM) than Co 2+ and Ni 2+ (IC 50 s ≈ 500 μM). 4. 4. While 4-AP increased the 45Ca 2+ content of whole synaptosomal preparations, no effect of 4-AP on 45Ca 2+ content was observed in lysed synaptosomal preparations. 5. 5. 4-AP-induced 45Ca 2+ uptake was inhibited by Cd 2+, Ni 2+ and Co 2+ in concentration ranges similar to those inhibiting 3H-DA release.
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